People's reliance on various electronic devices increases with the progress in the technological field. These electronic devices, such as computers and notebook computers, have internal elements that produce a large amount of heat during the operation of the electronic devices. The produced heat must be timely removed from the electronic devices to avoid the problem of overheated electronic devices. A cooling fan is usually provided in an electronic device for producing air flows and accordingly maintaining the electronic device at a specific operating temperature. However, there are times one single cooling fan is not sufficient to provide the required air flows. Therefore, two or more fans are frequently serially assembled together to provide sufficient air flows.
Taiwan Patent Publication No. 481434 discloses a Cooling Device for Central Processing Unit, which includes radiating fins and at least two fans and is characterized in that the at least two fans are serially connected end to end but spaced from each other by a plurality of connecting posts therebetween. The serial fan formed from two serially connected fans provides enhanced air flows and air pressure to more efficiently remove the high amount of heat produced by the central processing unit and absorbed by the radiating fins, and can therefore achieve an upgraded and quick cooling effect.
The cooling device for central processing unit disclosed in Taiwan Patent Publication No. 481434 also includes through holes provided at four corners of the fan frames of the two fans, so that screws can be threaded into the through holes to serially connect the two fans to one another and lock them to the radiating fins.
The problem in implementing the serial connection of two fans simply with screws lies in that the force used to tighten the screws is applied at points on one side of one fan instead of being applied on the contact surface of the two fans, which results in insufficient serial connection strength as well as noise produced during the operation of the serial fan. Meanwhile, air flows tend to leak via the space left between the two serially connected fans to adversely reduce the volume of air flows that can be acted on the radiating fins and accordingly reduce the heat dissipation performance of the serial fan.
According to another way of assembling a serial fan, one of the two fans to be serially connected together is provided at four corners with a plurality of through holes while the other fan is provided with at least one projection at positions corresponding to the through holes. By inserting the projections into the through holes, the two fans can be serially connected together and held in place. While this way enables two fans to fixedly connect to one another, the connection tightness between the two fans is poor to cause vibration and noise during the operation of the serial fan.
In brief, the prior art serial fans have the following shortcomings: (1) having poor connection tightness between the two serially connected fans; (2) producing vibration and noise during operation; and (3) using an inconvenient assembling manner.